By CONSTANCE L. HAYS

Published: April 18, 1998

Melissa Melchior was in a Manhattan deli the other night, standing before a refrigerator case filled with beer -- everything from Miller and Dos Equis to Pete's Bohemian Pilsner and Samuel Adams Cranberry Lambic. ''Actually, I've been meaning to try it,'' she said of the Cranberry Lambic, which would mean branching out from her usual Corona or Sapporo.

Miss Melchior, a 24-year-old sales clerk, does not pay attention to beer ads on television, does not worry much about price and drinks beer ''once in a while, because it has natural stuff in it that flushes you out.''

A few minutes later, in came Abel Quintana, 22, a stockbroker, who drinks Coors Light and Michelob Light. If he sees an appealing commercial, he might try that beer, as he did recently with Coors Light, he said. But he scoffed at craft beers -- stronger, often strangely flavored beers, usually made in small batches. ''Nobody wants to waste their time,'' he said. ''You drink it once and then, forget it.''

It is young people like these whose tastes America's brewers must decipher if they are to bring new life to a business now suffering from the twin terrors of essentially flat volume and abnormally low prices.

While the number of 21- to 27-year-olds, historically the biggest beer drinkers, has fallen by three million since 1990, demographers expect an upturn around 2000. But corralling those younger consumers -- who are both highly brand-conscious and notoriously lacking in brand loyalty -- will be a challenge, to put it mildly.

To do so, beer companies are sifting through demographic research and trying offbeat marketing and promotion ideas, embracing everything from quirky humor to cutting-edge travel offers.

''The brewers are having one heck of a time trying to figure this out,'' said John R. Matesich, chief executive for sales and marketing at the Matesich Distributing Company, a large beer wholesaler in Newark, Ohio. ''There are a lot of conflicting things going on out there that you just can't compartmentalize anymore.''

Given their current state of affairs, however, beer makers, whose sales are overwhelmingly domestic, are greeting the challenge with open arms. In 1997, the nation's beer business grew by just four-tenths of 1 percent. Volume remains below its level in 1990, before the excise tax of 1991 and when there were still plenty of new, young drinkers every year. In 1990, market shipments totaled 2.3 percent more than they did last year, according to Impact Databank, which tracks beer volume.

Then there is the decline in 21- to 27-year-olds -- from 27.6 million in 1990 to 24.6 million this year, according to Beverage Marketing, which maintains its own data base on beverage sales. Other age groups have not picked up the slack; sales of light beer and imports have grown, but other brands have lost ground.

''Young adult males in that age group are the target audience,'' said Dave Taylor, a spokesman for the Coors Brewing Company, which is trying to win them over with its ''Beer Man'' commercials and tie-ins to sports events.

These ''entry level drinkers,'' as they are known in the industry, are supposed to increase 14 percent the next five years.

But no one can say for certain what this generation will drink. They will have a wider array of choices -- from ubiquitous labels like Budweiser to price-sensitive imports to increasingly specialized craft beers. They are being called the most ad-resistant consumers yet, a description particularly disturbing to the beer industry, whose reliance on marketing is legendary.

''They're not very brand loyal because they see through all the advertising,'' said Steven A. Grasse, chief executive of Gyro Worldwide, a Philadelphia advertising agency that specializes in marketing to people ages 18 to 30.

It is not that they hate advertising -- quite the contrary. ''They look at advertising and marketing as almost a spectator sport,'' Mr. Grasse said.

Another question is how much the group will drink. The Anheuser-Busch Companies, which has 45 percent of the domestic beer market, appears to be banking on their drinking at least as much as their predecessors. In the company's latest annual report, the chairman, August A. Busch 3d, cited the demographic shift as one of ''a number of positive developments that further enhance Anheuser-Busch's long-term position as the world's beer company.''

But simply having more 21-year-olds in the mix is no guarantee of volume growth, others say. ''If these entry-level drinkers drink less, there may not be any great bump,'' said Benj Steinman, editor of Beer Marketer's Insights, an industry newsletter, who sees many young people turning away from alcoholic beverages because they believe it is bad to drink even moderate amounts. There are still plenty of college students, of course, who engage in binge drinking as a recreational sport.

Beer makers are confounded, Mr. Steinman added. ''Nobody knows exactly how to talk to these consumers,'' he said. ''It's a combination of their short attention span and the information glut.''